Large-volume containers are often used for holding, storing, and transporting bulk materials, such as powders, agriculture leaf and root crop products, metal castings, plastic resins, particulates, granular products, and many other materials. Generally, the containers provide sturdy walls that retain the bulk materials within the container and protect the bulk materials from entry of pests and contaminants while allowing the containers to be handled by equipment such as fork lift trucks and platen or clamp trucks during use or storage in warehouses and product manufacturing facilities and during transit. The containers are also often stacked multiple units high in storage and in truck trailers during transit.
One type of container useful for holding bulk materials assembles from elongated corrugated paperboard blanks. The blanks include spaced-apart scores for folding the blank to form separate panel of the container wall. A first blank defines the exterior surface of the container wall and a second blank defines the interior surface of the container wall. A plurality of rigid members attach around a perimeter of the panels of the first blank to provide vertical and horizontal supports and the two blanks laminate together. The laminated blanks fold on the scores and attach at opposing ends to define a tubular walled body having a cavity for holding the bulk materials. The exterior blank includes flaps that fold to form a bottom and may include flaps on an opposing edge to form a top.
Bulk leaf products typically are filled through tubes that enter the container and withdraw as the container fills. A ram forces the leaf products into a block having high density and under compression within the container. The leaf products contain moisture, and the block starts expanding as the ram withdraws. A top, such as top flaps on the container that fold relative to the wall, close the container. A plurality of spaced-apart straps tighten around the container and resist the top and bottom from opening by expansion of the contents of the container. The filled containers are placed in stacks in warehouses for the leaf products to dry. After a period of time, the leaf product is removed for processing. The container is typically re-used up to five or more times depending on the quality or condition of the container after use.
While these corrugated containers have long met a need in the container industry for storage and shipping of bulk materials, opportunities for changes and improvements have become apparent. The containers have wall panels that are about four feet in length (typically 45 inch panel lengths), and this necessarily requires elongated corrugated blanks of 180 inch length for folding to form the four wall panels of the container. Two production lines are used in the manufacture and assembly of the containers. In one line, blanks move on a plurality of rollers through a glue station and onto a plurality of rollers in an assembly station. A multi-person crew attach the rigid members to the adhesive on the exterior blank. Both cold adhesive and hot melt adhesive are used to secure the rigid members to the blank. Overglue that extends outwardly of the edges of the rigid members involves waste. The overglue may further stick to the rollers and drive belts of the manufacturing equipment. The glue and adhesives may then transfer as spots of glue and adhesive onto the blanks. Glue or adhesive spots on the surface wall of the interior blank that faces the bulk materials during use may result in rejection of containers as unsatisfactory for use. The elongated exterior blank with the attached wood members is heavy and awkward for picking up and turning over to position on the interior blank that moves on a second line through a glue station and an assembly station, and subsequent laminating of the exterior and interior blanks together. Because containers in use are often stacked, the containers must have sufficient top load compressive strength to support multiple units in a stack to prevent collapse of the lower containers. Further, notwithstanding the straps that attach after filling a container with a bulk material, contents expansion presses forcingly against the walls and such may result in buckling or bulging of the closure flaps. The bulging flaps have the potential for causing a stack of containers to tip, and a container that falls or a stack that tips over can cause injury to persons as well as loss of the product if the container bursts open because of the fall.
Accordingly, there is a need in the art for a bulk materials container that provides manufacturing and top load compressive strength improvements. It is to such that the present invention is directed.